1. Field of the Invention
This invention relates to protecting an elongate substrate, and more particularly to protecting an elongate substrate with a wraparound protective closure comprising a closure member in sheet form having a profiled transverse-edge which edge is enveloped when the closure is overlappingly wrapped around the substrate.
2. Discussion of the Art
Wraparound protective closures (i.e., wraparound sheets and tapes hereinafter referred to collectively as "sheets" or as "wraparound sheets") are widely used as protective closures in the pipe, electrical power distribution, and telecommunication industries for environmentally sealing and/or electrically insulating a pipe, conduit, cable, or the like. Wraparound sheets for elongate substrates have opposing transverse-edges by definition. When these closures are overlappingly wrapped around an elongate substrate, such as a pipe, conduit, cable, or the like, one transverse-edge is enveloped by the opposing transverse-edge. As the edges are overlapped, the thickness of the underlying layer causes the upper layer to ride up and over the underlying layer forming a bridge, thereby defining a gap or channel in which air can be trapped. This channel is a potential leak-path through which water may permeate and come into direct contact with the elongate substrate in need of protection, particularly if the channel is continuous.
The continuous-channel leak-path problem becomes especially pronounced when the wraparound sheet is fabricated of heat-shrinkable materials. The volume of air trapped as the overlapping edges create a gap, is believed to be augmented by air aspirated into the channel and trapped as dimensional-recovery elongates the bridge-gap. In the case of heat-shrinkable polymeric wraparound sheets for pipes which use mastics as a means to bond the sheet to the pipe, the problem has been observed to become significant at pipe diameters above 10 inches.
Numerous wraparound protective closures are known in the art, refer for example, to U.S. Pat. Nos. 3,455,336 to R. H. Ellis 3,574,313 to K. Tanaka, 3,770,556 to J. H. Evans et al., and 4,200,676 to Caponigro et al., and U.K. Pat. No. 1,506,242 to J. G. Robinson et al., all of which are herein incorporated by reference. Tanaka, Evans et al., and Robinson et al show wraparound sheets having profiled edges, respectively: tabs and slots for closure, slits to prevent buckling during heat recovery, and protrusions and recesses for interlocking engagement. None of these references addresses the channel leak-path problem.